micah: So, someone explain the basic idea of what people mean by this.

perry: Essentially, the concept is that the factor that led to the shutdown (lots of pressure from the Democratic base on Senate Democrats) and the decision itself to force shutdown were reminiscent of the GOP, the tea party and the 2013 shutdown.

natesilver: It feels like there are actually two interrelated concepts here:

Is the Democratic base becoming more “extreme” and less willing to compromise?

Are Democrats becoming more willing to use parliamentary tactics and otherwise push the boundaries of the rules to achieve those goals?

micah: Right, so let’s take those one at a time …

No. 1: Are Democrats more liberal? And, somewhat relatedly, are they less willing to compromise?

And do those answers depend on which Democrats you’re referring to? Elected officials, voters, etc.

clare.malone (Clare Malone, senior political writer): Well, more and more Democrats are identifying as liberal than ever before, I believe.

natesilver: There’s lots of evidence that Democrats are becoming more liberal, yes. Both voters and legislators.

harry: The answer to legislators is a bit more complex. There’s the argument for asymmetric polarization, that Republicans have become much more conservative but Democrats haven’t really become more liberal.

I don’t know if I buy that, however.

natesilver: I might have bought that four years ago, but it’s more dubious now.

micah: But isn’t the asymmetric argument that GOP legislators have grown more conservative than Democratic legislators have grown liberal? But that Democrats have still grown more liberal?

perry: I saw this as, in part, a story of the activist groups on the Democratic side becoming more aggressive, perhaps because the party’s voters overall are more liberal and the members in Congress have to be responsive to that. Here’s what I wrote after the shutdown was resolved:

I can’t say this for sure, but it’s hard to imagine even this brief shutdown happening without liberal groups like Indivisible and the hosts of the popular left-leaning Pod Save America imploring the party to take a strong stand on [the Deferred Action for Childhood Arrivals policy]. Pod Save America was carefully tracking whether Senate Democrats publicly committed to blocking the funding bill without DACA, and Massachusetts Sen. Elizabeth Warren tweeted Pod Save America’s hashtag #FightClub when she noted that she would oppose the legislation.

clare.malone: Wouldn’t 2018 be the year to accelerate the trend of liberalizing legislators?

micah: I 100 percent think the idea that President Trump would radicalize the Democratic Party makes a certain amount of sense.

clare.malone: I agree with that.

And then you had Sen. Bernie Sanders’ influence, which we really can’t discount — especially in the aftermath of Hillary Clinton’s loss. People seem more likely to advocate for his kind of progressive politics as an answer to Trump’s (initial) populist take on policy.

natesilver: I was talking to someone the other day who called Sen. Kirsten Gillibrand a moderate, based on her previous track record. But look at her voting record this year, and she has the lowest Trump score of anyone in the Senate. You can be really far left in a Bernie way, or really anti-Trump in a partisan way, or both, but it’s getting harder to get away with being moderate if you’re a prominent Democrat.

harry: The idea that Gillibrand is a moderate is the biggest load of malarkey I’ve ever heard. But I’ll let Silver go on here for a little.

natesilver: The guy I was talking to, who is conservative, was positing her as the more reasonable alternative to Sanders and Sen. Elizabeth Warren. But she’s still pretty darn liberal! The point is that everything has shifted to the left.

micah: She used to be more moderate, no?

harry: I think that’s not particularly true, Micah. She was for around five seconds as a member of the House. But yeah, Gillibrand is really quite liberal.

clare.malone: OK, but what was the larger point in all this? That more and more people are acting as Gillibrand did, right? Sensing a movement in the party to the left.

micah: Yes.

natesilver: One thing we haven’t seen as much is Democrats going after their moderates in red states. Sen. Joe Manchin has come under occasional scrutiny, but it hasn’t quite metastasized into anything.

clare.malone: Perhaps — especially during the first half of Trump’s tenure, with the GOP owning the government, basically — it’s more practical and rhetorically effective to be an insurgent politician rather than a compromiser if you’re looking to make headlines.

micah: OK, so let’s tackle the second part of that question now: There’s a bunch of evidence that the Democratic Party has become more liberal, but is there evidence that it’s become less open to compromise?

Second, as Nate said, I don’t think the Democrats who voted against the shutdown will be primaried, like what tends to happen on GOP side.

Democrats have become more like Republicans, but not in every way.

natesilver: I’d go back to those Trump scores again. Democrats aren’t providing much support to Republicans on anything, and especially not on key pieces of legislation. No Democratic votes for any version of the GOP health care and tax bills, for instance.

Republicans haven’t really tried to solicit their help, either.

But partisanship is less asymmetric and more bidirectional now. If stats like DW-Nominate aren’t showing that yet, I suspect they will within a few years

micah: Yeah, I’m not sure the Trump scores show that Democrats are unwilling to compromise; Republicans haven’t really offered them many legitimate compromises.

What Democrats haven’t adopted is the GOP’s policy intransigence. Where Republicans in the Obama years demanded absurd ransoms — like the complete defunding of the president’s signature legislative achievement — Democrats are asking Trump to accept the kind of deal he said he wanted all along, a deal key congressional Republicans have already embraced. The problem is that Trump refuses to make a deal.

perry: On Klein’s point … I’m not totally sure. DACA and Obamacare are such different issues. Would the Democrats block any Supreme Court nominee from Trump in 2024, if they controlled the Senate? I think so, now that the precedent has been set. I’m not sure. I think the amount of Democratic intransigence will depend on the issue.

natesilver: Maybe about 46 of the 49 Democrats would block any non-moderate Trump nominee? And you’d have some huge fights over the other three.

But, yeah, Republicans set a new precedent on SCOTUS and I don’t think there’s much turning back from it.

micah: But Klein is talking policy, not tactics (which we’ll get to in a sec).

clare.malone: Don’t you think that Democrats have to offer more concrete policy goals? For the more extreme Republican policies, you’d often have people asking to slash a program or slash a budget, you know?

perry: “The problem is that Trump refuses to make a deal.” I think “policy intransigence” is perhaps more of a feature of the Republican Party in general than the Democratic Party. The GOP is the party that believes in less government. I’m not totally sure Trump wants a deal on immigration. He has to say he wants a deal, because that’s what people in Washington are required to say.

I think the Freedom Caucus might prefer no solution at all, leaving the Dreamers in a kind of limbo, over voting for what could be cast as an amnesty, no matter how much border security is in the bill.

micah: Right, and Ezra’s point was that Democrats were still willing to add funding for border security and so on.

harry: I will say I think the House is different than the Senate and seems more liberal and less willing to compromise.

The vast majority of House Democrats voted against the funding bill on Monday.

micah: OK, so let’s talk tactics here.

clare.malone: Send ’em all to Elba.

micah: You could imagine a party getting more extreme ideologically but not more extreme tactically.

But maybe that’s possible in theory but not really in practice? Because Democrats do seem to be getting more extreme tactically, right?

natesilver: I think I agree, although you might want to define “extreme” in this context.

perry: The Democrats had basically a one-day shutdown. They did it reluctantly and stopped it quickly. That suggests to me that they are not ready to take the Republican path in that way. The shutdown was a more extreme move than I think they would have used in the past, but not quite as extreme as the GOP’s shutdown in 2013.

natesilver: I don’t think the shutdown entailed much if any political cost to Democrats. It may even have benefited them very slightly because Trump and the Republicans initially took more of the blame, and Democrats conceded before public opinion shifted too much. But the Democrats’ strategy also didn’t seem very well thought-out.

micah: Wait a sec, Perry, why is the Democratic shutdown less extreme than those GOP shutdowns?

Just because it ended more quickly?

perry: Sixteen days versus one day.

micah: But they still pulled the lever.

perry: The Republicans in 2013 had a position with with less than 40 percent public support and had a 16-day shutdown, Democrats had a position with more than 80 percent support and a had a one-day shutdown.

natesilver: There wasn’t 80 percent support for not passing a budget resolution until DACA was resolved, however. That had the potential to be a somewhat unpopular tactic.

harry: In fact, the tactic was unpopular. Per CNN, support for it was below 40 percent.

micah: I guess my point is that either way, they were willing to use government funding as leverage for a policy.

That’s crossing a line.

In other words, the tactic is the tactic — whether it has a ton of public support or none at all.

And the tactic is extreme.

natesilver: Not extreme compared to what Republicans did. Democrats are just playing by the new rules.

clare.malone: Yeah, it’s the rules that the Republicans set. That is, Democrats are slightly uncomfortable with the new paradigm but are learning to exist within it.

Republicans, since the paradigm is of their own creation, embrace its extremism with greater gusto.

micah: I can sign onto that.

natesilver: We arguably haven’t seen too many “innovations” from Democrats yet that Republicans didn’t try first, although former Senate Majority Leader Harry Reid killing the filibuster for non-SCOTUS nominees was one of them. With all that said, the filibuster isn’t in the Constitution, so I’m not sure it really qualifies as “extreme” to provide for majority rule in the Senate.

perry: More broadly, on tactics, do I think Democrats will, say, try to pass a bunch of laws that limit voting in a way that is likely to disproportionately affect white working-class voters? I do not. Or refuse to hold congressional hearings if they have an unpopular bill? Probably not.

I think that Democrats are getting more liberal. I’m not sure they will broadly get more aggressive on tactics. And that is likely to create a divide between the base and the party, which has been very visible since they ended the shutdown.

natesilver: Democrats could do more to liberalize voting laws, though. That’s been a pretty big blind spot for the party.

perry: Yeah, you might see more Democratic efforts to change political outcomes through policy, as you note. But I think they will be somewhat distinct from Republican tactics (making it easier to vote is different than making it harder).

natesilver: I agree as a matter of principle, Perry — I think there should be a Constitutional amendment to guarantee voting rights for American citizens — but as a matter of practice, expanding or contracting voting rights has long been “fair game” in politics.

I guess what I’m saying is that “extreme” isn’t a very helpful category. It’s more like … how aggressive is a party willing to be in pressing its partisan advantage.

perry: I get Nate’s point. But, and maybe I will be wrong, I’d bet that Democrats will be less aggressive in pressing partisan advantage, because I think they will be more squeamish about having the press or others criticize them about norms.

micah: OK, final thing I want to talk about: What’s causing the Democratic Party to become more hard-line, ideologically and tactically?

A shift in the Democratic voting coalition — away from a coalition and toward more of a movement like the GOP?

A shift in the Democratic voting coalition — younger voters are more and more of the base, and more liberal?

Democrats just following Republicans’ lead?

A reaction to Trump?

Losing, as Clare says?

Something else?

natesilver: I think it’s mostly No. 3. Democrats looking at the GOP example and coming to believe that it was a sucker’s bet to not treat politics as a zero-sum game.

clare.malone: I think it’s Nos. 4 and 5. Democrats have tended to get more radically left in reaction to Trump, and they’re embracing hardline tactics because they’ve lost a lot of their power and need to gin up some momentum.

harry: It’s Nos. 3 and 4.

micah: See … I think it’s No. 1.

natesilver: Perry’s comment about Democrats being “more squeamish about having the press or others criticize them” is relevant too. Obama — at least at the start of his term — tried to position himself as a “post-partisan” figure who was Inherently Reasonable and always on the Right Side of History.

I don’t mean to say that Obama had an ineffective presidency overall, but I’m not sure his thesis worked.

perry: I think Nos. 1-5 are all relevant, and No. 6 might be that Democrats have come to view Obama as someone they admire who maybe wasn’t tough enough. And they don’t want to repeat that mistake.

harry: I think they’re all good answers.

micah: Harry is such a wimp.

harry: I’m weak. I admit it.

micah: I’m surprised you all see this as so driven by elected officials, rather than them reacting to voters.

natesilver: Hmm, am I saying that? I think elected officials are mostly leading from behind.

clare.malone: Dude. I wrote, “Democrats have tended to get more radically left in reaction to Trump” — that’s voters!

micah: OK, OK.

Take it easy!

clare.malone: No, gotta stir the pot!

perry: I think its elite-driven.

perry: I doubt that Democrats care about immigration more than Republicans do solely because Democrats have more Latinos in their coalition. White Democratic voters are now more liberal on racial issues, which I think is driven by elites.

natesilver: It may be elites > rank-and-file Democratic voters > elected officials.

clare.malone: Think you’re misreading. I think it’s Women’s March-type groups that have formed (Indivisible, etc.), and the party’s realization that they ignored the progressive base that Sanders appealed to. It’s a culture on the left that’s embraced Black Lives Matter, etc.

And the elected officials are saying, “Oh, progressivism is hot right now!”

It’s grassroots, not elite-driven, in short.

Trickle-up politics.

natesilver: THE HOTTEST CLUB IN THE DEMOCRATIC PARTY IS DEMOCRATIC SOCIALISM!

perry: I view Indivisible as elites, and the women’s marches as led by elites.

natesilver: The modal grassroots Democrat voted for Clinton last year, not Bernie.

micah: This is a really good debate and one we should continue. But we’re running out of time. First, I’m realizing I really should have invited Julia Azari to this chat. So, let’s get a quick political science interlude …

Julia, we’ve been debating whether Democrats have gotten more extreme ideologically and tactically (and the consensus seems to be yes). Do you have any thoughts about why that’s happened?

julia_azari (Julia Azari, political science professor at Marquette University and FiveThirtyEight contributor): Yes. I am not sure which ones are correct but let me offer two that are at least not egregiously wrong.

First: Trump. This has already been said. I think as the Democratic coalition gets more diverse and also more attuned to race and immigration issues (because of efforts by activists, which I don’t think was on the original menu), it’s become harder to engage in the kind of racial compromise that’s been common in U.S. political history — as I said in my piece on Friday. (New rule: I get to promote my pieces when I get drafted into a chat at the last minute.)

micah: That’s fair.

perry: lol.

julia_azari: Second: Obama.

The party moved left under Obama for a bunch of reasons. Some are things Obama talked about and emphasized. But I’d also suggest that things that didn’t go as well under Obama — racial injustice wasn’t solved, economic inequality wasn’t either — are important to many Democrats, and that they are still problems post-Obama has led to a push for a different kind of party.

micah: Thank you!

OK, closing thoughts?

natesilver: Since we’re running out of time, I guess I don’t have time to post my troll-ish question about whether Republican tactics have actually been effective.

perry: How are the Republicans not effective? They control everything!

micah: Let’s end on that trollish question, Nate.

natesilver: This is a devil’s advocate case, but one could raise points such as the following: Republicans could have won a lot more Senate seats in 2010/2012 if it hadn’t been for the tea party challenges. They haven’t gotten all that many major policy objectives passed. Republicans had electoral wins — quite a few — but a lot of them come from the Electoral College and from gerrymandering/districting advantages and from the way those things tend to overrepresent the white, rural vote, not the GOP’s parliamentary tactics. And now they have Trump, who may be a one-termer and who may otherwise be a huge liability.

Again, it’s not totally convincing.

But if the GOP gets decimated in 2018 and/or 2020, people are going to think about this era a lot differently.

Nate Silver is the founder and editor in chief of FiveThirtyEight. @natesilver538

Clare Malone is a senior political writer for FiveThirtyEight. @ClareMalone